Method for joining aluminum structures



Patented Oct. 19, 1943 METHOD FOR JOINING ALUMINUM STRUCTURES Kenton D.

New York McMahan, Scotia, N. Y., assignor to General Electric Comp any,a corporation ol' Application December 15,1941, Serial No. 422,99'i

Claims.

The present invention relates to a method for joining metals havingsubstantially the same aluminum is cast around a solid aluminumstructure an oxide film on the solid aluminum prevents fusion of thecast and solid metal. If a flux is employed in such a process, forexample in joining an aluminum fan blade to a supporting aluminumstructure by casting the supporting structure about the fan blade, thereis a tendency to form a bond at the extreme end of the blade but theflux is merely added to the oxide layer on the blade and prevents fusionbetween the molten and the solid metal,

, and furthermore causes corrosion between the parts which eventuallyresults in failure of the joint.

One of the objects of the present invention is to provide an eicient andreliable method for obtaining strong. sound junctions between metalstructures having substantially equal melting points and particularlybetween aluminum or aluminum alloy structures. appear hereinafter.

The novel features which are characteristic of my invention are setforth with particularity in the appended claims. My invention, however,will best be understood from reference to the following specificationwhen considered in connection with the accompanying drawing in whichFig. 1 is a cross sectional view of an aluminum fan blade positioned ina sand mold and embodying the features of my invention; Fig. 2 is across sectional view of the same blade after molten aluminum has beenpoured into the mold; Fig. 3 is a cross sectional View of a modifiedform of my invention; Fig. 4 is a view partly in elevation and partly incross section of the fan blade and mold shown in Fig. 3; While Fig. 5 isa fan constructed in accordance with my invention.

In carrying out my invention, a structure which may be an aluminum fanblade I is positioned in a sand mold 2. In operation the blade I may besupported at opposite ends thereof Further objects will` as indicated inFig. 5 of the drawing. The extreme outer end of the blade II is providedwith a somewhat bulbous portion 3 which is shown as triangular in shapein Fig. 1 but may be any desired form. The part 3 is joined to the bladeproper by means of a reduced, very thin section or junction 4. Ifdesired. a small amount of flux 5 may be applied to the lower surface ofthe part 3, as indicated in Fig. 1, to facilitate transfer of heat fromthe molten metal into that part.

The problem of making the blade I fuse into a molten mass of aluminum isprimarily one of heat transfer across an oxide layer and of heatconduction away from the junction 4 and through the blade I. Where ablade is employed which has a bulbous or dovetailed outer end portion 3connected to the main body of the blade by a very narrow or thin sectionof metal asindicated in Fig. 1, the greatly reduced volume of metal inthe narrow section substantially isolates the enlarged portion 3 fromthe main body of blade I with respect to thermal conductivity. Thiseffect in combination with the ilux coated portion of the part 3 resultsin complete melting of that part when molten aluminum 6 is poured intothe sand mold 2 and around the portion 3 of the blade. The oxide coatingon the blade proper is thereby broken and the line of contact betweenthe blade and molten metal widens tothe full thickness of the blade, asindicated by the shaded portion of Fig. 2 with the result that the endportion of the blade fuses into the molten metal and sets with itthereby forming a strong, durable bond.

During fusion, the oxide layer on the aluminum is pushed to the outersurface of the cast aluminum as indicated at 1 in Fig. 2 of the drawing.At this point the oxide layer is without harmful effect. When theenlarged or dovetailed portion 3 is completely melted any ilux 8 whichhas been applied to the outer surfaces will float to the outer surfaceof the cast aluminum as indicated in Fig. 2 and may be removed by acleaning or machining operation.. In Figs. 1 and 2 the fan blade I isshown as having a somewhat enlarged portion 9 adjacent its outer endprovided with opposite parallel grooves I0 and II. It is unnecessary,however, to employ either grooves or an enlarged section.

In Figs. 3 and 4 there is disclosed a substantially flat blade I2. Theouter or lower end of this blade is provided with a yseries of closelyadjacent punched-out portions I3 which give the eiect of a thin neckeddown or dovetailed section. When molten aluminum is poured around theouter end of the table I2 the thin sections Il act in substantially thesame manner as the reduced section 4 shown in Fig. 1.

The word "aluminum as employed in the present specification and claimsis intended to include aluminum base alloys as well as aluminum.Furthermore, while the present method is illustrated in connection withaluminum or aluminum alloys it may be employed in joining other metals.The metals to be joined, however, should have substantially the samemelting point.

What I claim as new and desire to secure by Letters Patent of the Unitedstates, is:

1. The method of joining two aluminum struc- 'A tures which comprisesproviding a bulbous portion connected to the main body portion through areduced section of metal to thereby substantially thermally isolate saidbulbous portion from the main body portion of said structure.positioning said aluminum structure in a mold and pouring moltenaluminum around said reduced section and bulbous portion.

2. The method of joining two aluminum structures which comprisesmaterially reducing the volume of metal in one of said structuresadjacent one end thereof to thereby provide a greatly restricted passagefor heat transfer between the end body portion and main body portion ofsaid structure, positioning said structure in a mold and pouring moltenaluminum into said mold to thereby surround and melt said end portion.

3. 'I'he method of joining two aluminum structures which comprisesmaterially reducing the volume of metal in one of said structuresadjacent one end thereof to thereby substantially thermally isolate saidend portion of said structure from the main body portion thereof,positioning said structure in a mold and pouring molten aluminum thereinto thereby melt said end portion and reduced portion of said structure.

4. The method of joining two aluminum structures which comprisesmaterially reducing the volume of metal in one of said structuresadjacent one end thereof to thereby substantially thermally isolate saidend portion of said structure from the main body portion thereof,positioning said structure in a mold and pouring molten aluminum aroundsaid reduced portion and the portions of said structure adjacent theretowhereby said molten metal when cooled forms an integral structure withsaid first-mentioned structure.

5. The method of joining two metal structures having substantially equalmelting points which comprises providing one of said structures with anauxiliary portion integrally connected with the main body portion ofsaid structure by a thin section of metal which substantially thermallyisolates said auxiliary portion from said main body portion, positioningsaid structure in a mold and pouring molten metal around said auxiliaryportion to thereby melt said auxiliary portion and a portion of saidmain body portion.

KENTON D. MCMAHAN.

